1. Field of the Invention
This invention relates to an optical write apparatus and optical write method for writing an image displayed on an image display screen onto an image record medium onto which an image is written upon application of light for representing the image.
2. Description of the Related Art
With the recent rapid advance and widespread use of computers, relevant machines, and the information communication environment with Internet mobile communications as the nucleus, the effects of information digitalization are widely recognized and IT revolution is taking place. Digital information is used exceeding the time and space on various scenes of business, public, and privacy and our life styles are largely affected.
As information digitization is advanced, the total distributed information amount and digitalized information ratio rapidly rise and the variety of content is increased. As the information environment is improved, the productivity is enhanced; on the other hand, the efficiency of the cycle of selecting significant information from among enormous information pieces, understanding the information, and determining and acting according to the information is also demanded more than ever before. In such environment change, the development of electronic displays indispensable as an interface for connecting digital data and human beings was the base of constructing the information environment, needless to say, and the role of the electronic display grows more than ever before.
On the other hand, paper media also continue to serve as information display media beside displays. It is expected that if paperless society is placed in an advanced state with the development of information electronization, paper consumption is decreased; in fact, however, there is a trend toward an increase in the consumption amount of information paper. The following causes are possible: Large change in the practice of distributing information in paper form does not occur; occasions of printout are also increased in association with an increase in distributed electronized information; print is easy to perform and transient information and documents being edited are printed readily (output increase of transient documents); a large number of persons find it inconvenient to conduct a sequence of jobs only with a display without using paper; the whole productivity is improved because of information electronization; and the like. If paper consumption also increases worldwide in association with the digital information distribution amount increased more and more in the future, an important social issue is also caused to occur in the sense of conservation of the global environment, and it is also necessary to consider dealing with the issue.
Considering the described background, an image record medium called digital paper or electronic paper having the merits of both an electronic display and paper is proposed as one form of information display media demanded in the future information-oriented society. Clear definition about the technical field does not exist; for example, to attach importance to the form and characteristics like paper and add digital functions containing rewrite, (1) (microcapsule) electrophoretic technique, (2) two-color particle rotation control technique, (3) ferroelectric liquid crystal technique, (4) guest host liquid crystal technique, (5) toner display technique, (6) cholesteric material technique, and the like are proposed as display media technologies, and research and development containing bringing some to the commercial stage is underway.
Every technique mentioned above is reflection type display and has a memory property of being capable of holding an image without continuing to apply energy such as voltage once the image is written, and can be made flexible. The techniques are common in orientation at this point in time, but an ideal technical candidate comprising all of high image quality as much as print, moving image suitability, highly reliable memory property, flexibility like paper, color suitability, low price, and the like does not appear and each of the techniques has its merits and demerits.
The characteristics required as image record media include stable rewritability, resistance to mechanical load, additional writability, and the like in addition to the above-mentioned items; among them, a function of rendering information viewed on a display the form like a sheet supported by hand instantaneously can be named as an important function that cannot be provided simply by properly using a display and printout paper. Using a plurality of sheets, the flexibility of listing and spatial placement provided by paper can be supported and these characteristics are provided, whereby interference with thinking and debating and fatigue and wasted paper consumption can be prevented and intellectual work is helped. At this time, if the price per sheet of electronic paper is high, the function of helping the intellectual work is impaired because it becomes difficult to have a plurality of sheets, readiness to handle paper is impaired, the distribution property like paper is impaired, etc. Therefore, image record media that can provide the above-described function at a low price are demanded.
To provide the above-described function, namely, the function of rendering information viewed on a display the form like a sheet supported by hand instantaneously, the following two ways are possible: a) using a sheet-like display comprising display and drive elements placed integrally without any change and b) using a drive that can be separated from a display sheet to write and separate the sheet.
As for a), it is indispensable to provide one drive per screen, resulting in an increase in the cost per sheet. To output a high-resolution image required for practical document read, etc., a drive circuit capable of accomplishing high-definition and high-speed driving needs to be formed on a sheet-like substrate, and the practical level is not reached in the present technology. If the technique is accomplished with the development of the thin-film transistor formation technology on a film substrate, it is difficult to provide an environment in which a plurality of sheets are handled readily because of an increase in costs.
As for b), a display sheet and a drive are separated from each other, whereby an increase in the cost per sheet can be prevented and practical section capable of supporting use of a plurality of sheets is provided. However, if a technique in which the color (reflectivity) change speed of each display element is low or a sequential write technique with one-dimensional elements in write operation is adopted, it takes time in output and instantaneous rewrite cannot be supported. Therefore, instantaneous write with two-dimensional drive elements becomes necessary and further to separate the display sheet and the drive rapidly, a connection device such as a connector needs to be extremely simple. As a specific method for providing such a function, an optical write image record medium using the candidate technology in (6) described above and a photoconductor in combination is proposed in JP-A-2000-111942, Nihon Gazou Gakkai Japan Hardcopy 2000 Ronbunshuu p 89-92. According to the technique, a wiring pattern in pixel units is not required for a medium and if applying a predetermined voltage to transparent electrodes on a pair of substrates and applying a two-dimensional light pattern from the outside of the medium are performed at the same time, an image can be formed instantaneously. The medium and the voltage applying unit are connected only at two points as many as the number of the electrodes and can be attached and detached very easily. To use the technology to actually apply a two-dimensional light pattern, for example, a liquid crystal panel or a projector can be used.
To display information of a document or a picture prepared with a personal computer, etc., on an image display such as a CRT or a liquid crystal display and convert the displayed information into media (hardcopy media) to enable the user to view the displayed information with several media supported by hand, it is common practice to print out on paper. In addition, information displayed on a screen is photographed by an instant camera, etc., and is converted into a film. In any case, it requires a predetermined time and thus there is a problem of interrupting thinking and lowering the efficiency of creative work.
In recent years, the expectation with respect to new hardcopy media replacing paper has been raised from environmental problems of the conservation of forest resources and waste treatment. From such a background, the research of new image record media of optical write record media described above is conducted heavily. For example, an image record medium comprising a display layer made of a cholesteric material and an optical switching layer made of amorphous silicon is known as described in H. Yoshida, T. Takizawa et al. “Reflective Display with Photoconductive Layer and a Bistable, Reflective Cholesteric Mixture” SID' 96 APPLICATIONS DIGEST p 59-p 62, and an image input system comprising each liquid crystal element having a memory property and an organic photoconductor deposited on each other is known as described in Japan Hardcopy' 96 Fall Meeting p 25.
usually, with the image record media of the optical write record media, while a predetermined voltage is applied to an optical switching layer, the impedance of the optical switching layer is changed based on the received light amount and the voltage applied to a display layer is controlled, whereby the display layer is driven for displaying an image.
As display materials used for the display layer of such an image record medium, liquid crystal materials such as nematic liquid crystal, twist nematic liquid crystal, supertwist liquid crystal, and smectic liquid crystal, surface stabilization ferroelectric liquid crystal, polymer-scattered liquid crystal comprising liquid crystal material scattered in polymer, capsuled liquid crystal comprising capsuled liquid crystal material are known in addition to the cholesteric material. Among them, to use a display material having a memory property, electric power is not required for holding the record display state, so that after image information is recorded and displayed, the image record medium can be separated from the writer and can be carried. As such display materials having a memory property, cholesteric material, ferroelectric liquid crystal, polymer-scattered liquid crystal, capsuled liquid crystal, and the like are available.
A display screen of a CRT or a liquid crystal display can be instantaneously recorded on (transferred onto) the image record medium using a cholesteric material. As compared with printout to paper or photographing with an instant camera, etc., the time in preparing a hardcopy may be shorter and interrupting of thinking is lessened and lowering the efficiency of creative work is prevented. The environmental problems of the conservation of forest resources and waste treatment can also be solved.
An information terminal (called information kiosk terminal) being installed in a public installation, a shopping mall, etc., becomes widespread. It has an image display screen displaying an image and a touch panel and the user touches directly a menu button of the touch panel, whereby he or she can view various pieces of information on the floors, for example, on the image display screen. With the information kiosk terminal, the user selects information out of an information selection screen of a menu by performing direct or indirect instruction operation on an operation screen and visually checks the selected and displayed information and then memorizes the result or takes notes or if a printer is contained, prints out on paper and carries the paper. If the information amount is small, the information is easy to memorize; however, as the information amount increases, there is a problem of taking time and labor writing the information in longhand. If it is possible to print out on paper, the print wait time on paper is long, the person unfamiliar with computer operation is hard to know how to operate the machine for printing out the display screen information, and paper resources are wasted for temporary use. Then, the image display screen of the information kiosk terminal is instantaneously written onto the image record medium using a cholesteric material described above, whereby the above-mentioned problem can be solved.
To apply a two-dimensional light pattern according to the technique proposed in JP-A-2000-111942, Nihon Gazou Gakkai Japan Hardcopy 2000 Ronbunshuu p 89-92, it is important to form or project a clear light pattern on a photoconductive layer of the image record medium during writing onto the image record medium regardless of the method using a liquid crystal panel or a projector. As an actual procedure for instantaneously writing an image onto the image record medium, while the user visually checks the image displayed on the liquid crystal panel or the projector and switches the image, etc., he or she instantaneously makes a screen copy onto the image record medium as required.
Generally, to visually display an image, light from the top of the screen (the top of the liquid crystal panel or the top of the projector display panel) needs to have a constant dispersion property and enable the user to recognize the image over a given viewing angle. On the other hand, to write an image onto the image record medium, a light pencil having a high resolution to apply collimated light rather than dispersion property needs to be applied onto the surface of the photoconductive layer. That is, when an image is visually checked and when an image is written onto the image record medium, optically different characteristics are required. Usually, the liquid crystal display uses a backlight of a diffused light source so as to enhance viewability and the projector uses an enlargement optical system to project the optical pattern of an image on a dispersive display panel for creating a dispersive image. With both the machines, to provide the optical pattern to view, the image which becomes finally dispersive is created. To use an image record medium write apparatus and a separate display in combination, the optical function may be separated, but two two-dimensional optical pattern production panels become necessary, resulting in an increase in costs and upsizing. The sense of copying only the favorite part of the viewed portion intact onto the image record medium is lost.
FIG. 1 is a conceptual drawing of the basic configuration and write of an optical write image record medium, FIG. 2 is a conceptual drawing for using a liquid crystal write apparatus, and FIG. 3 is a conceptual drawing for using a projector.
FIG. 1 shows the basic configuration of the image record medium and the write light application direction. The configuration is proposed in Nihon Gazou Gakkai Japan Hardcopy 2000 Ronbunshuu p 89-92 mentioned above. An image record medium 10 of the image record medium comprises a display layer 13 of cholesteric material and a photoconductor layer (organic photoconductor layer) 15 deposited on each other via a light absorption layer 14 between paired substrates 11 and 17 containing transparent solid electrodes 12 and 16. To make possible AC driving of liquid crystal, charge generation layers 151 and 153 are placed above and below a charge transport layer 152 as the photoconductor layer 15 so that a symmetrical carrier move can be made. To write, write light for representing an image based on a two-dimensional strength distribution is applied to the photoconductor layer 15 and a constant pulse voltage is applied between the electrodes 12 and 16. Then, in the portion to which strong light is applied, the impedance of the photoconductor layer 15 is lowered by optical pumping under an electric field and the partial pressure onto the display layer 13 is increased. If a proper pulse voltage considering the threshold value of the cholesteric material display layer 13 is applied, switching is performed between a focal conic phase (transparent) and a planar phase (selective reflection color) in response to the applied light amount in the cholesteric material. A two-dimensional dimmer element is used with the write apparatus, whereby an image can be instantaneously transferred to the image record medium upon batched light exposure.
FIG. 2 shows a related art example wherein a liquid crystal panel 20 is used as a write apparatus. With the write apparatus, a light pattern is applied to the image record medium 10 based on whether or not backlight passes through the portion of a liquid crystal layer 21 formed with the light pattern like an image. At this time, a write pulse voltage from a pulse generator 30 is given to the image record medium 10.
To suppress the light dispersion component from the backlight, an LED having directivity can be used as the backlight. In this case, however, even if the image record medium is not placed, light output from the panel has high directivity, of course; the write apparatus is not fitted for that also serving as a display directly viewing the light.
FIG. 3 shows an application example wherein a projector 40 is used as a write apparatus. A light pattern from the projector formed with the light pattern like an image is applied intact to the photoconductive layer of the image record medium 10. If the image record medium is not placed, the write light pattern cannot be recognized as an image unless it strikes some object and is dispersed.
In both examples in FIGS. 2 and 3, the image record medium is placed and write light is applied from the rear of the display face. The display output by the liquid crystal panel or the projector cannot directly be observed from the display face (the surface of the image record medium (top face in FIG. 1)) in the presence of the light absorption layer (black) 14 in the image record medium (see FIG. 1). After the rewrite operation is performed, display is produced on the image record medium. Therefore, the configuration of this portion can deal with only typical rewrite operation such as page turning and image change cannot be recognized under circumstances where input frequently changes, and thus a separate display becomes necessary.
The image record medium requires optimum drive signal for the liquid crystal layer to write and screen display. However, write onto the image record medium is performed in the state of image display to view and thus is not always performed in the state fitted for the write condition; this is a problem. It may be difficult to provide an image suited for viewing with respect to the finally provided gradation representation, color, etc., of the image record medium because of the characteristic difference between the image record medium and the image write apparatus. Further, the display mode of the size, font, etc., of the image displayed on the screen of a CRT or a liquid crystal display may be unfitted for the image record medium picked up for viewing. It is difficult to deal with various image record media developed one after another based only on the characteristics of the image write apparatus and drive signal. Further, with the image record medium of double-page spread type, if the display screen of an image display is simply transferred, there is also the disadvantage for viewing that the left and right or the top and bottom are reversed.
Further, to instantaneously write the image display screen of an information kiosk terminal onto an image record medium, the problems of taking time and labor writing the information in longhand, the print wait time on paper, and unfamiliarity with computer operation are solved, but information provided in the recent information kiosk terminal may be used not only in the installation in which the information kiosk terminal is placed, but also in various facilities; information kiosk terminals appropriate for such a case are demanded.
It is therefore an object of the invention to provide an optical write apparatus and an optical write method for making it possible to satisfy the demand for the optically different characteristics of light dispersion in visual observation of an image and light transmission in writing an image onto an image record medium and enhance the display quality of the image written onto the image record medium.